Research, product, and drug development in the chemical and pharmaceutical industries rely heavily upon synthetic chemistry and separation science. Chromatographic separation processes rely upon the differential partitioning of solute molecules between a solid or stationary phase and the mobile phase that is passed through the chromatographic matrix. Individual sample components are separated from each other because each molecule or ion has a different affinity for the stationary phase. Components that have a low affinity for the stationary phase will migrate faster through a chromatographic matrix than those components that have a high affinity for the stationary phase. In some cases the affinity between solute components and the stationary phase is so great that there may be no migration at all of the component through a matrix that has a significant concentration of binding sites available. The differential affinities of sample components to the stationary phase lead to differential rates of migration through the column. Each component exits the column at a different time and this time differential can be exploited for analytical purposes or for purposes of collecting the purified components. The separation efficiency is determined by the amount of spreading of the respective solute bands as they pass through the chromatographic matrix.
In hypothetical analyses of separations in a chromatographic column, those knowledgeable in the field consider a plurality of connected and hypothetical zones or theoretical plates that contain mobile phase, stationary phase and component solutes in concentrations that vary in time and in space as a chromatographic separation occurs. The number of theoretical plates in a chromatographic column is calculated from its actual performance with a component molecule. The number of theoretical plates for a component molecule is proportional to the affinity of the stationary phase for the analyte divided by the width of the peak of the component band emerging from the column. It is of great importance in the field of chemical separations to have columns with large numbers of theoretical plates, and columns with efficiencies exceeding 100,000 plates per meter are becoming readily available to enable workers to perform difficult separations. It is also of great importance to reduce the time required for chromatographic separations. Unfortunately, the rate of equilibrations that occur between the stationary phase and solute molecules are severely limited by the nature of existing chromatographic matrices, and band spreading and loss of resolution occur if separations are attempted at high flow velocity. This problem forces workers in the field to make a difficult choice between the time costs of slow analyses and the performance costs of decreased resolution.